JPS61151216A - Production of heat-resistant methacrylate resin composition - Google Patents

Abstract

PURPOSE:To obtain the titled composition excellent in transparency, heat distortion resistance and mechanical properties, by polymerizing methyl methacrylate and maleic anhydride to a specified conversion and adding an aromatic vinyl compound to the reaction mixture. CONSTITUTION:A monomer mixture comprising maleic anhydride (A) and 1.5-50 pts.wt., per pt.wt. component A, methyl methacrylate (B) is mixed with, if neces sary, 2-35wt%, based on the mixture, aromatic vinyl compound and 0-1.0mol%, based on the mixture, mercaptan, and the resulting mixture is polymerized to a conversion of 30-70%. 100pts.wt. obtained polymer is mixed with 2-100pts. wt. at least one aromatic vinyl compound (C) and, optionally, 0.0001-10wt%, based on the total monomer, radical polymerization initiator, other comonomers, a plasticizer, a crosslinking agent, etc. The resulting mixture is polymerized to a conversion which is by at least 10% higher than that before the addition of component C, and volatile components are removed from the reaction product to obtain the titled composition comprising 1-20wt% units of component A, 40-97wt% units of component B and 2-40wt% units of component C.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a heat-resistant methacrylic resin composition, and more specifically, a method for producing a methacrylic resin composition that is transparent, has little coloring, and has a high heat distortion temperature. Regarding.

(Prior art) In general, methacrylic resins whose main component is methyl methacrylate have excellent optical properties, weather resistance, etc., and also have well-balanced performance in mechanical properties, thermal properties, moldability, etc. It is used in a wide range of fields such as automobile parts, displays, lighting parts, signboards, nameplates, electrical equipment parts, and optical transmission equipment parts. There are many fields in which heat resistance is restricted, and therefore there is a strong demand for improved heat resistance.

Therefore, research has been widely conducted to improve the heat resistance of methacrylic resins, such as methyl methacrylate, α-methylstyrene, etc. described in JP-A-56-81322,
The method of copolymerizing styrene and maleic anhydride is actually an excellent method, and the present inventors have already proposed a method for producing these resins with excellent productivity (Japanese Patent Application No. 59-3117).

However, currently commercially available maleic anhydride contains stabilizers for the purpose of reducing thermal coloring and improving thermal stability. A subsequent study revealed that there was a difference in the color tone of the final resin, which was inconvenient in terms of raw material procurement and inventory management.

Further, when a polymerization reaction product using maleic anhydride is devolatilized in the devolatilization step, if the amount of remaining maleic anhydride is large, the equipment becomes complicated, which is a disadvantage in industrial production. As a method for reducing the amount of residual maleic anhydride in the polymerization reaction product, the copolymerizability of maleic anhydride is increased by increasing the ratio of styrene and/or α-methylstyrene to maleic anhydride. Although it is possible to reduce the amount of residual maleic anhydride, simply changing the composition of the monomers has the problem of lowering mechanical strength and increasing shelf life.

(Problems to be Solved by the Invention) The purpose of the present invention is to overcome the problems of the prior art as described above, and to reduce the characteristics such as excellent optical properties, mechanical properties, and moldability inherent to methacrylic resin. without letting
An object of the present invention is to provide a method for producing a heat-resistant methacrylic resin composition with excellent productivity.

(Means for Solving All Problems) The method for producing the heat-resistant methacrylic resin composition of the present invention comprises 40 to 97% by weight of methyl methacrylate units, 1 to 20% by weight of maleic anhydride units, and 2 to 20% of aromatic vinyl compound units. To produce a methacrylic resin composition consisting of 35% by weight, first, a monomer mixture containing methyl methacrylate and maleic anhydride as essential components is polymerized to a polymerization rate of 30 to 70%, and then the polymerization reaction product is A monomer containing at least one aromatic vinyl compound as an essential component is added to the polymer, and after polymerization is performed such that the polymerization rate is 10% or more higher than before the addition, volatile components are removed. shall be.

A feature of the production method of the present invention is that conventionally, when copolymers with different compositions are mixed, the resulting resin loses transparency, but By adding a specific amount of monomer to the polymerization reaction product so as to limit the proportion of each unit of It is possible to obtain a heat-resistant methacrylic resin composition with good transparency, low discoloration, and excellent mechanical properties in which the maleic acid content is greatly reduced.

The methyl methacrylate unit in the methacrylic resin composition obtained by the method of the present invention is a necessary component to maintain the optical, weather resistance, or mechanical properties inherent in the methacrylic resin, and is 40 to 97% by weight in the composition. If it is less than 40% by weight, physical properties such as weather resistance will be impaired, and if it exceeds 97% by weight, no improvement in heat resistance can be expected. In addition, maleic anhydride units are essential for improving heat resistance, and their proportion is 1 to 20% by weight.
If it is less than 1% by weight, improvement in heat resistance is insufficient, and if it exceeds 20% by weight, too much maleic anhydride remains in the reaction solution to obtain the desired composition.

Further, the aromatic vinyl monomer is a component mainly for improving the copolymerizability of maleic anhydride, and is a component for improving the copolymerizability of maleic anhydride.
If it is less than 40% by weight, the copolymerizability of maleic anhydride cannot be improved, and if it exceeds 40% by weight, it will cause a decrease in optical properties and mechanical properties.

The aromatic vinyl compound unit constituting the composition obtained by the method of the present invention can be selected from styrene, α-methylstyrene, chlorostyrene, vinyltoluene, and the like.

When the aromatic vinyl compound unit is composed of styrene or vinyltoluene, the composition ratio in the composition is 45 to 97% by weight of methyl methacrylate unit, 2 to 35% by weight of styrene or vinyltoluene unit, and 1 maleic anhydride unit. It is in the range of ~20% by weight. In addition, when the aromatic vinyl unit is composed of styrene and α-methylstyrene units, the composition ratio in the composition is 40 to 97 methyl methacrylate units, 1 to 1 styrene unit.
20% by weight, 1 to 20% by weight of α-methylstyrene units and 1 to 20% by weight of maleic anhydride units.

The method for producing the composition according to the present invention can be roughly divided into two steps: a polymerization step and a volatile matter devolatilization step.

In the polymerization step, first, a polymerization raw material consisting of a monomer mixture containing methyl methacrylate and maleic anhydride as essential components and a mercaptan is fed into a polymerization reactor.
A step of polymerizing to a polymerization rate of 70%, then adding a monomer containing at least one aromatic vinyl compound as an essential component to the polymerization reaction product and polymerizing it to increase the polymerization rate by 10% compared to before addition. It is. The volatile matter devolatilization process is a process in which unreacted monomers and other volatile substances are separated and removed from the polymerization reaction product containing the monomers produced in the polymerization process to obtain a resin composition. In the polymerization step, a monomer mixture containing mercaptan-containing methyl methacrylate and maleic anhydride as essential components is supplied to a polymerization reactor and polymerized. The ratio of methyl methacrylate to maleic anhydride to be supplied cannot be determined unconditionally depending on the polymerization conditions, but the weight ratio is 1.5 to 5.
It is in the range of 0, more preferably in the range of 2-20.

In the present invention, the monomer mixture supplied to the polymerization reactor contains methyl methacrylate and maleic anhydride as essential components, but aromatic vinyl compounds may be added as long as they do not impede the purpose of the present invention. It can also be added in an amount of 2 to 65% by weight in the monomer mixture.

In the present invention, mercaptan can also be used for the purpose of adjusting the degree of polymerization. The mercaptans used include primary, secondary and tertiary mercaptans having an alkyl group or a substituted alkyl group, such as n-butyl, isopropyl, n-octyl, n-dodecyl, 5ec-butyl,
5ec-dodecyl, tert-butyl mercaptan; aromatic mercaptans such as phenylmercaptan, thiocresol, 4-tert-butyl-0-thiocresol; thioglycolic acid and its alkyl esters; alkyl esters of β-mercagutoprobionic acid toso ; Examples include mercaptans having 2 to 18 carbon atoms such as ethylene thiocricol. These can be used alone or in combination of two or more. Of these mercaptans, tert-butyl, n-butyl, n-octyl and n-dotesyl mercaptan are preferred.

The amount of mercaptan used ranges from 0 to 10 molar.

If it exceeds 1.0 mol%, the degree of polymerization will decrease and the mechanical properties of the product will decrease.

The monomer mixture consisting of methyl methacrylate and maleic anhydride is polymerized to a polymerization rate of 30-70%.

A polymerization rate of less than 50% is unfavorable from an economic point of view;
A copolymer with a wide composition distribution is easily obtained, and if it exceeds 70 cm, the viscosity of the polymerization reaction product becomes high, causing problems in stirring and mixing.

Next, in the polymerization step of the present invention, the polymerization rate obtained above is 3.
A monomer containing at least one aromatic vinyl compound as an essential component is added to 0 to 70% of the polymerization reaction product, so that the overall polymerization rate is 1.10% or more than the polymerization rate before addition. Polymerizes to become If the increase in the polymerization rate after addition is less than 10%, the proportion of unreacted maleic anhydride in the polymerization reaction product cannot be reduced, and this is also disadvantageous in terms of economy. The amount of the aromatic vinyl compound to be added is not particularly limited, but is 2 to 10 parts by weight per 100 parts by weight of the polymerization reaction product.
It is in the range of 0 parts by weight. In the method of the present invention, when the aromatic vinyl compound is added to the polymerization reaction product, the composition ratio of unreacted monomers in the polymerization reaction product is such that the composition ratio of unreacted monomers in the polymerization reaction product contains at least 50 moles of methyl methacrylate, and the mole of maleic anhydride is When the number is α and the number of moles of aromatic Birul is γ, γ
/α-12 to 6 is the mechanical property,
Results are given in terms of transparency and copolymerizability of maleic anhydride. In the present invention, as the aromatic vinyl compound, among the above-mentioned compounds, it is particularly preferable to use styrene, α-methylstyrene, and vinyl toluene color. When these are used, the ratio to maleic anhydride is preferably in the range shown by the following formula.

(β1+15βt) > 1-sα(1,5β, +
β, )〈6α However, α = number of moles of maleic anhydride β1 = number of moles of styrene or vinyltoluene β, = α
- Number of moles of methylstyrene The method of the present invention preferably uses bulk polymerization or solution polymerization. Examples of solvents used when solution polymerization is employed in the method of the present invention include benzene, toluene, xylene, ethyl sulfate, acetone, methyl ethyl ketone,
Examples include methyl isobutyl ketone, dimethylformamide, cyclohexanone, and tetrahydrofuran. One or more of these can be used, and the amount used is in the range of 1 to 50% by weight based on the total amount of monomers.

If the amount of solvent used exceeds 50% by weight, industrial productivity will decrease.

The polymerization temperature in bulk polymerization and solution polymerization is 50 to 150°C before adding the aromatic vinyl compound to the polymerization reaction product.
It is preferable to maintain the temperature more preferably in the range of 70 to 140°C. Below 50°C, a large amount of polymerization initiator is required;
If the temperature exceeds 150°C, it becomes complicated to control the polymerization rate and the equipment becomes complicated. On the other hand, the polymerization temperature after addition of the aromatic vinyl compound is 50 to 150°C if the residual maleic anhydride in the polymerization reaction product is 1% by weight or more, and 50 to 220°C if it is less than 1% by weight. Good.

Although the method of the present invention can be carried out without using a polymerization initiator depending on the monomer composition ratio and polymerization conditions, it is advantageous to carry out the method using a radical polymerization initiator. Examples of the radical polymerization initiator used include di-tert-butyl peroxide, dicumyl peroxide, and di-tert-butyl peroxide.
t-butyl perphthalate, di-tort-butyl-
perbenzoate, tert-butyl peracetate,
2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-amyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and lauroyl peroxide Organic peracids such as azobisisobutanol diacetate, 1.1-azobiscyclohexanecarbonitrile, 2
-Phenylaso2.4-Dimethyl-4-methoxyvaleronitrile, 2-cyano-2-propylazoformamide and azo compounds such as azobisisobutyronitrile are mentioned. These radical polymerization initiators can be used alone or in combination of two or more.

The amount of radical polymerization initiator used is 0 based on the total monomer.
．． 0 O01-10% by weight, preferably 0,005-1
Weight%. If it is less than 0.0001% by weight, the polymerization rate will be slow, which is disadvantageous in terms of production, and if it exceeds 10% by weight, it will cause deterioration in physical properties and coloration of the resulting resin.

The polymerization apparatus used in the method of the present invention is not particularly limited, and various types such as a seed type, tower type, control type, and duct type can be mentioned, but it is possible to ensure uniform polymerization reactivity within the polymerization reactor. From the viewpoint of maintaining properties, a reactor selected from a complete mixing type reactor, a plug glow type reactor, and a combination thereof, which can perform sufficient stirring and mixing, is preferable.

When using these polymerization apparatuses, either a batch method or a continuous method can be applied to the polymerization.

Since the polymerization reaction product produced by the method described above contains volatile components such as unreacted monomers and/or solvents, most of the volatiles are separated and removed by subsequent heating under reduced pressure. Alternatively, the residual monomer content can be adjusted to a predetermined amount by dissolving, reprecipitating, or drying. Equipment used to remove volatiles includes, for example, conventional vent extruders or other tevolatizers.

The resin composition that has been volatilized and separated is extruded in a molten state through a die or the like and molded into a desired shape for use.

In the method of the present invention, depending on the variety and quality requirements, small amounts of other comonomers may be used in combination, plasticizers,
Crosslinking agents, heat stabilizers, colorants, ultraviolet absorbers, mold release agents, etc. can also be added.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.
In the examples, ``chi'' represents weight %.

The physical properties of the resin compositions in Examples were evaluated using the following method.

(1) Heat deformation resistance Bicat softening temperature (vs.
p) (°C) was measured.

(2) Total light transmittance ASTM-D-1003 (3) Tensile strength and elongation ASTM-D-638 (4) Composition analysis It was determined by infrared spectrophotometry, acid value titration, etc.

(5) Color tone and transparency of injection molded plate Visually (6) Intrinsic viscosity It was determined by measuring in chloroform at 25°C.

(7) Melt index ASTM-D-1258 260°C, load 58 fkg The symbols used in the tables of Examples represent the following compounds.

MMA + methyl methacrylate α-Meat: α-methylstyrene St + styrene MAH + maleic anhydride AI + n-octyl mercaptan A2 + t-dodecyl mercaptan B1 + lauroyl peroxide B2F1.1-bis(t-butylperoxy)-3,3
, 5-trimethylcyclohexane B3 1 di-t-butyl peroxide 01 + methyl ethyl ketone C2 = ethylbenzene MA + methyl acrylate Examples 1 to 3, Comparative Examples 1 to 3 A polymerization stock solution (1) having the composition shown in Table 1 was prepared. This was placed in a 10 t polymerization reactor with a pressure resistant 10 kg agitator, and was polymerized by maintaining it at the temperature and time shown in Table 1 under conditions substantially excluding oxygen, and then using a pressure pump to carry out the polymerization shown in Table 1. The stock solution (2) was heated to 60°C and added, and Table 1
Further polymerization was carried out under the conditions shown below. 1 10 minutes before the end of polymerization
The temperature was raised to 40°C. Continued temperature 180℃, vacuum pressure 10
A polymer was obtained by processing with a volatile matter separation and removal device held in a TM Hfabs. This polymer was crushed and passed through a small twin-screw extruder with two vent holes to give a
5°C, vent pressure 5 ttm Hfabs.

It was shaped by devolatilizing extrusion under the following conditions. This pellet was evaluated and its physical properties are shown in Table 2.

In Example 4, the polymerization stock solution (1) shown in Table 2 was polymerized under the conditions shown in Table 2 using the same equipment as in Example 1, and then the polymerization stock solution (2) was added and mixed, and the polymerization stock solution (2) was added to both ends through a sampling tube. Inner diameter with pulp t25cytr x 30c
The polymerization reaction solution was poured into a stainless steel tube and polymerized for 4 hours at 160° C. The results are shown below.

Example 5 A first reactor consisting of a uniformly stirred tank with a reaction volume of 401, followed by a static mixer and connected to it L/D=
20. A device consisting of a plug flow type second reactor with an internal volume of 201 and a three-stage vented extruder as a devolatilization device was used. The additional polymerization stock solution (2) was continuously metered and injected under pressure using a small pump just before the static mixer.

The composition of polymerization stock solution (1) is 66 parts of methyl methacrylate, 10 parts of styrene, 2 parts of α-methylstyrene, 12 parts of maleic anhydride, 0.4 parts of lauroyl peroxide, 0.11 parts of n-octyl mercaptan, and 3 parts of ethylbenzene.
The mixture was mixed in a mixing tank while bubbling nitrogen to substantially remove oxygen, and transferred to a hold tank sealed with nitrogen, from which it was continuously supplied to the first reactor. The first reactor was operated at a temperature of 80° C. and an average residence time of 4 hours. The polymerization reaction product taken out from the first reactor had a polymerization rate of 51% and had the following composition.

Polymer composition: Methyl methacrylate units 614 styrene units
14.4% α-methylstyrene units
1 unit of maleic anhydride 15.1 units Next, 6 parts of methyl methacrylate, 2 parts of styrene, 2 parts of α-methylstyrene, and 11 parts of lauroyl peroxide were added to the above polymerization reaction product taken out from the first reactor. .01
1.0 parts of heavy metal g(2) consisting of 0.02 parts of t-butylbaroxypenzoate and 8 parts of ethylbenzene.
The mixture is added at a rate of 8t/hour and mixed, and the mixture is supplied to the second reactor, with an inlet temperature of 80°C and an outlet temperature of 140°C.
Polymerization was carried out by gradually raising the temperature so that Steady state (1
After 6 hours), the polymerization rate of the polymerization reaction product at K was 90.

The composition of unreacted monomers in the polymerization reaction product supplied to the second reactor was as follows.

Methyl methacrylate 70.4% styrene
1t4-α-methylstyrene
65% maleic anhydride 117%
The polymerization reaction product taken out from the second reactor was transferred to the first vent at 160°C and 500 Torr; the second vent at 210°C.
, 10 Torr; 3rd vent 230°C, 5 T
A pellet of the resin composition was produced by removing volatile matter by passing it through a devolatilizing extruder held at .

The physical properties of the obtained resin composition are shown below.

Composition of resin composition: Methyl methacrylate units 66.9% styrene units 14.0 t α-methylstyrene units 4
, 71% Maleic anhydride units 14.4% Remaining monomer: Methyl methacrylate 0.3% Intrinsic viscosity (
azzv): n, 55 Melt Intex +2.11F/10 minutes heat deformation resistance (
VBP)+136°C On the other hand, when the polymerization was repeated under these polymerization conditions without adding the polymerization stock solution (2), white cloudy spots appeared on the molded product of the obtained resin composition.

(Effects of the Invention) As detailed above, the heat-resistant methacrylic resin composition of the present invention has excellent transparency, heat deformation resistance, coloration, mechanical properties, etc. Molded products such as parts, electrical parts, optical discs, lenses, etc.
It is useful for applications such as optical fibers and sheet materials such as signboards.

Claims (1)

[Claims] In producing a methacrylic resin composition consisting of 40 to 97% by weight of methyl methacrylate units, 1 to 20% by weight of maleic anhydride units, and 2 to 40% by weight of aromatic vinyl compound units, first methyl methacrylate and maleic anhydride are essential components. 30-70% of the monomer mixture
Polymerization was carried out to a polymerization rate of , and then a monomer containing at least one aromatic vinyl compound as an essential component was added to the polymerization reaction product, and polymerization was carried out so that the polymerization rate was 10% or more higher than before the addition. 1. A method for producing a heat-resistant methacrylic resin composition, the method comprising: then removing volatile components.